典型氢氧化细菌固碳特性种间差异及胞外有机物对固碳过程影响

Interspecific differences of carbon fixation characteristics of typical hydrogenoxidizing bacteria and effects of extracellular organic compounds on carbon fixation process

化能自养细菌对全球CO_(2)固定具有重要的意义.研究了4种典型氢氧化细菌(HOB,分别是Alcaligenes hydrogenophilus DSM 2625、Pelomonas saccharophila DSM 654、Variovorax paradoxus DSM 30034和Acidovorax facilis DSM 649)的固碳特性及其种间差异性,并探究了胞外游离有机碳(EFOC)对不同种类HOB固碳效率差异性的影响.结果表明:(1)不同HOB自养培养过程中表观固碳量随时间呈显著差异性,其中,DSM 2625生长速度较快,其平均固碳量分别是DSM 654、DSM 649和DSM 30034的6.30、8.76和7.02倍.(2)不同HOB之间cbb L基因转录量与表观固碳量的相关系数为0.980(p<0.05),cbb L基因转录量是造成不同菌种之间表观固碳效率差异的关键因素.(3)HOB细胞蛋白质含量与cbb L基因丰度和转录量之间也存在显著正相关,相关系数分别为0.999(p<0.01)和0.976(p<0.05),即化能自养细菌CO_(2)同化途径所固定的有机碳进一步参与细胞蛋白质的合成,进而影响其生长速度和表观固碳效率.(4)HOB在自养培养过程中产生的EFOC对cbb L基因转录效率产生反馈抑制作用,且不同HOB之间,EFOC/TOC比例越低,表观固碳效率越高.

Chemoautotrophic bacteria play a vital role in global CO_(2) fixation.The carbon fixation characteristics of four typical hydrogen-oxidizing bacteria(HOB),including Alcaligenes hydrogenophilus DSM 2625,Pelomonas saccharophila DSM 654,Variovorax paradoxus DSM 30034 and Acidovorax facilis DSM 649 and their interspecies differences were studied,and the effects of extracellular free organic carbon(EFOC)on the variability of carbon fixation efficiency of mentioned HOB species were also investigated.The results showed that:(1)The apparent carbon fixation yield of different HOBs showed significant variability during the autotrophic culture process.Among them,DSM 2625 grew fast and the yield of average carbon fixation yield was 6.30 times,8.76 times,and 7.02 times greater that of DSM 654,DSM 649,and DSM 30034,respectively.(2)The correlation coefficient between cbb L gene transcription level and apparent carbon fixation yield in different HOBs was 0.980(p<0.05),which demonstrated the transcription level of cbb L gene was the key factor on the difference in apparent carbon fixation efficiencies of the four strains.(3)The remarkable positive correlations between HOB cell protein content and cbb L gene abundance and transcription level,which were 0.999(p<0.01)and 0.976(p<0.05),respectively,indicating that organic carbon fixed by the CO_(2) assimilation pathway of chemoautotrophic bacteria was further involved in cell protein synthesis and subsequent affected their growth rate and apparent carbon fixation efficiency.(4)The EFOC produced by HOB during autotrophic culture exerted a feedback inhibition on cbb L gene transcription efficiency,and the lower the EFOC/TOC ratio,the higher the apparent carbon fixation efficiency among different HOBs.